Optical brightening agents

ABSTRACT

Optical brightening agents for use in textiles, paper, detergents correspond to the formula ##STR1## where R, R 1  are preferably derived from amino-acids, particularly glutamic and iminodiacetic acids.

This invention relates to novel organic compounds based on4,4'-diaminostilbene-2,2'-disulphonic acid.

4,4'-diaminostilbene-2,2'-disulphonic acid., known generally as "DAS",is the starting material for a number of important products used inindustry, most importantly various dyestuffs and optical brighteners.DAS-based optical brighteners (OBAs) find a wide range of uses indetergents, paper, textiles and so on.

One of the standard ways of making an optical brightener is tosubstitute the amino groups of DAS with substituted triazines. This maybe done, for example, by reacting DAS with cyanuric chloride and thenfurther reacting the remaining chlorines on the cyanuric chloridemoiety. A popular substitutent for one of these chlorines is provided bysulphanilic acid.

It has now been found that it is possible to make a new class ofDAS-based compounds whose performance is substantially better than thatof known sulphanilic acid-based materials. The invention thereforeprovides a compound in free acid or salt form of the formula I ##STR2##wherein R, R₁ are moieties which are the same or different and have theformula -NR₂ R₃,

wherein:

(a) R₂ is selected from

(i) hydrogen;

(ii) C₁₋₆ alkyl, optionally substituted with at least one of mercapto,C₁₋₆ thioalkyl, OH and SO₃ M; and

(iii) --R₄ (CO₂ M)_(x)

wherein R₄ is an aliphatic moiety having from 1-6 carbon atoms, thosevalencies not bonded with groups CO₂ M being bonded with at least one ofH, mercapto, C₁₋₆ thioalkyl, OH and SO₃ M, x is an integer of from 1-4and M is selected from hydrogen, a colourless cation or an amine-derivedcation;

with the proviso that, when R₂ is selected only from (i) or (ii), anygroup (ii) is substituted with at least both of OH and SO₃ M;

(b) R₃ is selected from groups R₂, hydrogen and C₃₋₆ alkyl, with theprovisos that R₂ and R₃ cannot both be hydrogen, and when one of R₂, R₃is hydrogen, the other cannot be --(NHCH₂ CO₂ H);

or R₂ and R₃ together with the nitrogen atom form a ring having from 5-6members only one of which is heterocyclic, which ring is singlysubstituted with --COOM or --SO₃ M; and R₅ are selected independentlyfrom the group consisting of hydrogen, methyl, C₁₋₆ alkoxy and halogen.

In a preferred embodiment of the invention, R₅ is hydrogen and thesulphonic acid groups on the phenylene rings attached to the triazinerings are meta or para to the connecting amino groups, that is, theparticular moieties attached to the triazine rings are derived fromsulphanilic acid or metanilic acid.

The moieties R and R₁ may be derived from any-suitable compounds knownto the art. It is preferred that they be amino-acid residues. Examplesof suitable acids include glycine, aspartic acid, serine, hydroxyglutamic acid and alanine, but the preferred acids are glutamic acid andiminodiacetic acid.

The most preferred compounds are those derived from metanilic acid orsulphanilic acid and where R is derived from glutamic or iminodiaceticacid.

In the case where R₂ and R₃ together with the nitrogen atom of groups R,R₁ form a ring, it is preferred that this ring be a pyrollidine ringsubstituted with --COOM.

The compounds according to the invention may be prepared in free acidform or in salt form such as with an alkali metal cation, an organicamine salt, a mixed or partial salt.

The materials M are preferably either metal cations, particularly sodiumand potassium, or simple alkanolamines such as mono-, di-andtriethanolamine.

Two of the most preferred compounds have the formulae II and III##STR3##

Other compounds which also perform well are those which have theformulae IV-XI ##STR4##

The compounds according to this invention may be prepared by standardsynthetic methods using readily-obtainable reagents.

The compounds may be used individually or in admixture. It has beenfound that some of them, particularly the aminodiacetic acid/glutamicacid -sulphanilic acid-derived material referred to hereinabove, exhibitoutstanding optical brightening characteristics. The compounds accordingto the invention are therefore very useful as optical brightening agents(OBAs) in paper, textiles and so on.

The compounds of the invention are particularly effective when used asoptical brightening agents for paper. They may be applied to papereither by addition to a paper stock prior to sheet formation or -theymay be incorporated into a coating composition which is subsequentlyapplied to a paper sheet. Incorporation into a size which is then usedon paper is particularly effective. The compounds may also be applied tothe surface of the paper in conjunction with certain additives which arewell known to boost the performance of the optical brightening agents,such as: carboxymethyl cellulose, polyethylene glycols, alkanolamines,polyvinyl alcohols etc.

The invention therefore provides a process for making paper comprisingthe addition of a compound of formula I to a paper stock.

Furthermore, the invention provides a process for making papercomprising the addition of a compound of formula I to a paper coatingcomposition.

Still further the invention provides a process for treating textilescomprising the addition of a compound of formula I thereto.

The invention also provides paper comprising a compound of formula I andfurthermore textiles comprising a compound of formula I.

Still further the invention provides the use of a compound of formula Ias an optical brightener for detergents, paper or textiles, preferablyin coating methods after paper sheet formation.

The invention is further described by reference to the followingnon-limiting examples, in which all parts are expressed by weight.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph charting whiteness against optical brightening agentconcentrations in g/l.

FIG. 2 is a graph charting whiteness against optical brightening agentdosage as a % of dry pigment.

PREPARATION EXAMPLE

Preparation of a compound according to Formula III.

Stage 1

A solution of 18.4 parts of cyanuric chloride in 100 parts of acetone isallowed to run into a mixture of 300 parts of crushed ice and 500 partsof water, while cooling. A solution of 20.7 parts of the sodium salt of4,4'-diamino-2,2' stilbenedisulphonic acid in 150 parts of water is thenintroduced dropwise into this mixture at a temperature in the range of0° to 5° C. and the reaction mixture is kept weakly acid to Congo paperby adding sodium bicarbonate. Stirring is continued at 0° to 5° C. untilno primary aromatic amine group is detectable by diazotization.

Stage 2

A solution of 19.6 parts of sulphanilic acid sodium salt in 200 parts ofwater is added slowly to the reaction mixture from Stage 1, keeping thetemperature at 5° to 10° C. and the pH at neutral by simultaneousaddition of dilute sodium hydroxide solution. When the addition iscomplete, the mixture is heated to 50° C. and stirring is continueduntil no primary aromatic groups can be detected by diazitization.

Stage 3

15 parts of glutamic acid is added to the reaction mixture from Stage 2and the mixture is heated to reflux. The pH is kept at 8 by addition ofdilute sodium hydroxide solution during this process. The acetone isallowed to distil off and the mixture is refluxed for 5 hours. Thereaction mixture is concentrated and salt is added to precipitate theproduct. The product is filtered off and washed with 10% brine.

Application Example 1

10 parts of the compound of formula III is dissolved in 50 parts ofdistilled water. 100 parts of a typical size-press starch is made up in1000 parts of water and cooked at 90° C.

It is then cooled to 60° C. The brightener solution is then incorporatedinto the starch solution. A paper base or board is surface coated withthe starch/brightener solution in the size-press or film-press and driedat 80°-120° C. in the drying section of the paper machine.

A paper or board with a considerably improved degree of whiteness isthus obtained.

Application Example 2

An aqueous solution of the compound of formula III is dosed understirring into a warm (60° C.) solution of an anionic oxidised potatostarch ("Perfectamyl" (trade mark) A4692), together with water to give astarch solution of 5% and a known amount of compound.

The brightened starch solution is then poured between the moving rollersof a laboratory size-press (forming a pond) and a paper base sheet (acommercial white paper 75 g/m², neutral sized, CIE Whiteness 72, withouta size-press coating) is then passed between the rollers, through thesolution. The paper coated with the wet starch solution is then driedfor 5 minutes at 70° C. in a flat bed drier.

The paper is weighed before application and whilst wet to determine thepick-up of wet starch solution and therefore the pick-up of starch.

Once dried, the paper sheets are allowed to condition, and the CIEWhiteness (W₁₀) of each sheet is then calculated from measurements madeon a calibrated spectrophotometer.

The process is repeated with an equal amount of a commercially-availableOBA ("Leucophor" (trade mark) U) substituted for the compound accordingto the invention.

The resulting CIE Whiteness values for the compound and the commercialproduct on the paper are shown in the graph of FIG. 1. The degree ofWhiteness W₁₀ is calculated from the formula (from ISO 105-502).

    W.sub.10 =Y.sub.10 +800(0.3138-x.sub.10)+1700(0.3310-y.sub.10)

The superior performance of the compound according to the invention isnoticeable from low proportions of compound

Application Example 3

An aqueous solution of a compound of formula III is dosed understirring, into a coating composition (described below) together withwater to give a constant solids content and a known amount of thecompound. The brightened coating composition solution is then coated onto a suitable base paper using an automatic wire-wound bar applicatorwith a standard speed setting and a standard load on the bar. The papercoated with the solution is then dried in a hot air flow for 5 minutes.A known area of the paper is weighed before application and after dryingto determine the coating weight applied.

Once dried, the paper sheets are allowed to condition, and the CIEWhiteness (W₁₀) of each sheet is calculated from measurements made onthe same calibrated spectrophotometer.

The coating composition recipe is:

    ______________________________________    Pigment:-China Clay SPS                       100        parts    Water              64.4       parts    Dispersing agent.sup.1                       0.6        parts    Latex.sup.2        20         parts    20% Starch solution.sup.3                       25         parts    Solids content approx. = 55%    ______________________________________     .sup.1. "Polysalz" (trade mark), a sodium salt of a polyacrylic acid, is     used     .sup.2. "Acronal" (trade mark) S320D, an acrylic ester copolymer, is used     .sup.3. "Perfectamyl" A4692

The experiment is repeated using the same quantity of acommercially-available optical brightening agent. The results are shownin the graph of FIG. 2. Again, it can be seen that the compound of thepresent invention performs significantly better than that of thecommercial optical brightening agent.

We claim:
 1. A compound in free acid or salt form of the formula I##STR5## wherein R, R₁ are moieties which are the same or different andhave the formula --NR₂ R₃,wherein: (a) R₂ is selected from(i) hydrogen;(ii) C₁₋₆ alkyl, optionally substituted with at least one of mercapto,C₁₋₆ alkylthio, OH and SO₃ M; and (iii) --R₄ (CO₂ M)_(x) wherein R₄ isan aliphatic moiety having from 1-6 carbon atoms, those valences notbonded with groups CO₂ M being bonded with at least one of H, mercapto,C₁₋₆ alkylthio, OH and SO₃ M, x is an integer of from 1-4 and M isselected from hydrogen, or a colourless cation;with the provisos that,when R₂ is selected only from (i) or (ii), any group (ii) is substitutedwith at least both of OH and SO₃ M; (b) R₃ is as defined in R₂ with theproviso that R₂ and R₃ cannot both be hydrogen, and when one of R₂, R₃is hydrogen, the other cannot be --(CH₂ CO₂ H);or R₂ and R₃ togetherwith the nitrogen atom form a pyrrolidine ring, said ring is singlysubstituted with --COOM or --SO₃ M; and R₅ is selected from the groupconsisting of hydrogen, methyl, C₁₋₆ alkoxy and halogen.
 2. A compoundaccording to claim 1, wherein R₅ is hydrogen and the SO₃ M groups on thephenylene rings attached to the triazine rings are meta or para to theconnecting amino groups.
 3. A compound according to claim 1, wherein R,R₁ are residues of amino-acids.
 4. A compound according to claim 3,wherein the amino-acids are selected from the group consisting ofglycine, aspartic acid, serine, hydroxyglutamic acids, alanine, glutamicacid and iminodiacetic acid.
 5. A compound according to claim 1, havinga formulae selected from the group consisting of the formulae II andIII. ##STR6##
 6. A method of producing an optically brightened paper ortextiles, or an optical brightener containing detergent comprising thestep of adding the compound of formula I, as claimed in claim 1, to amember selected from the group consisting of detergents, paper, paperstock, paper coatings and textiles.